Functional polymorphism at position 677 in gene coding for methylene tetrahydrofolate reductase (MTHFR), a rate limiting enzyme in methyl cycle, was shown to alter MTHFR activity and DNA methylation in human placenta, which further increases 3.5-fold risk of premature rupture of membranes in BV positive women (265). The gene discussed is MTHFR; the disease is bacterial vaginosis.